'''
二叉树遍历方式
    前序遍历
    中序遍历
    后序遍历
    层次遍历
'''
class BiTreeNode:
    def __init__(self,data):
        self.data = data
        self.lchild = None  # 左孩子
        self.rchild = None  # 右孩子

a = BiTreeNode('A')
b = BiTreeNode('B')
c = BiTreeNode('C')
d = BiTreeNode('D')
e = BiTreeNode('E')
f = BiTreeNode('F')
g = BiTreeNode('G')

e.lchild = a
e.rchild = g
a.rchild = c
c.lchild = b
c.rchild = d
g.rchild = f

root = e

from collections import deque
# print(root.lchild.rchild.data)
def pre_order(root):  # 前序遍历
    if root:
        print(root.data,end=',')
        pre_order(root.lchild)
        pre_order(root.rchild)

def in_order(root):
    if root:
        in_order(root.lchild)
        print(root.data,end=',')
        in_order(root.rchild)

def post_order(root):
    if root:
        post_order(root.lchild)
        post_order(root.rchild)
        print(root.data,end=',')

def level_order(root):
    queue = deque()
    queue.append(root)
    while len(queue) > 0:
        node = queue.popleft()
        print(node.data,end=',')
        if node.lchild:
            queue.append(node.lchild)
        if node.rchild:
            queue.append(node.rchild)


pre_order(root)
print('')
in_order(root)
print('')
post_order(root)
print('')
level_order(root)